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Date: Wed, 26 Aug 2020 18:26:36 +0200 From: Heiner Kallweit <hkallweit1@...il.com> To: Sascha Hauer <s.hauer@...gutronix.de>, netdev@...r.kernel.org Cc: Andrew Lunn <andrew@...n.ch>, Florian Fainelli <f.fainelli@...il.com>, kernel@...gutronix.de Subject: Re: [PATCH] net: mdiobus: fix device unregistering in mdiobus_register On 26.08.2020 11:51, Sascha Hauer wrote: > __mdiobus_register() can fail between calling device_register() and > setting bus->state to MDIOBUS_REGISTERED. When this happens the caller > will call mdiobus_free() which then frees the mdio bus structure. This > is not allowed as the embedded struct device is already registered, thus > must be freed dropping the reference count using put_device(). To > accomplish this set bus->state to MDIOBUS_UNREGISTERED after having > registered the device. With this mdiobus_free() correctly calls > put_device() instead of freeing the mdio bus structure directly. > > Signed-off-by: Sascha Hauer <s.hauer@...gutronix.de> > --- > drivers/net/phy/mdio_bus.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/drivers/net/phy/mdio_bus.c b/drivers/net/phy/mdio_bus.c > index 0af20faad69d..85cbaab4a591 100644 > --- a/drivers/net/phy/mdio_bus.c > +++ b/drivers/net/phy/mdio_bus.c > @@ -540,6 +540,8 @@ int __mdiobus_register(struct mii_bus *bus, struct module *owner) > return -EINVAL; > } > > + bus->state = MDIOBUS_UNREGISTERED; > + > mutex_init(&bus->mdio_lock); > mutex_init(&bus->shared_lock); > > I see the point. If we bail out after having called device_register() then put_device() has to be called. This however isn't done by mdiobus_free() if state is MDIOBUS_ALLOCATED. So I think the idea is right. However we have to call put_device() even if device_register() fails, therefore setting state to MDIOBUS_UNREGISTERED should be moved to before calling device_register().
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